Answering Amen before putting on the Tefillin
Question
Shalom Rav, A person began putting on tefillin, recited the blessing on the arm-tefillin, and then, before reciting the blessing on the head-tefillin, answered Amen to another blessing that he heard. What should he do?
Answer
Shalom u’vracha.
One who has the custom to recite a separate blessing on the head-tefillin, “al mitzvat tefillin” – if he spoke between the arm-tefillin and the head-tefillin, he recites two blessings on the head-tefillin: “lehaniach tefillin” and also “al mitzvat tefillin.”
One who has the custom not to recite a separate blessing on the head-tefillin, and relies on the blessing “lehaniach tefillin” said over the arm-tefillin, if he spoke between them, then on the head-tefillin he recites only the blessing “al mitzvat tefillin.”